package com.binbinyl.utils;

import android.util.Base64;
import java.security.MessageDigest;
import java.security.spec.AlgorithmParameterSpec;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

/**
 * Created by b-doing on 2017/8/14.
 */

public class AesUtils {


    private final Cipher cipher;

    private final SecretKeySpec key;

    private AlgorithmParameterSpec spec;

    public static final String SEED_16_CHARACTER = Constants.INTERFACE_AES_KEY;

    public AesUtils() throws Exception {

        // hash password with SHA-256 and crop the output to 128-bit for key

        MessageDigest digest = MessageDigest.getInstance("SHA-256");

        digest.update(SEED_16_CHARACTER.getBytes("UTF-8"));

        byte[] keyBytes = new byte[32];

        System.arraycopy(digest.digest(), 0, keyBytes, 0, keyBytes.length);

        cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");

        key = new SecretKeySpec(keyBytes, "AES");

        spec = getIV();

    }

    public AlgorithmParameterSpec getIV() {

        byte[] iv = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,};

        IvParameterSpec ivParameterSpec;

        ivParameterSpec = new IvParameterSpec(iv);

        return ivParameterSpec;

    }

    public String encrypt(String plainText) throws Exception {

        cipher.init(Cipher.ENCRYPT_MODE, key, spec);

        byte[] encrypted = cipher.doFinal(plainText.getBytes("UTF-8"));

        String encryptedText = new String(Base64.encode(encrypted,

                Base64.DEFAULT), "UTF-8");

        return encryptedText.replaceAll("\r|\n", "");

    }

    public String decrypt(String cryptedText) throws Exception {

        cipher.init(Cipher.DECRYPT_MODE, key, spec);

        byte[] bytes = Base64.decode(cryptedText, Base64.DEFAULT);

        byte[] decrypted = cipher.doFinal(bytes);

        String decryptedText = new String(decrypted, "UTF-8");

        return decryptedText;

    }
}
